From the Guidelines
POCUS has a sensitivity of 88.2% for detecting necrotizing fasciitis, making it a valuable diagnostic tool in emergency situations. When performing POCUS for suspected necrotizing fasciitis, key findings to look for include diffuse subcutaneous thickening accompanied by fluid accumulation of > 4 mm in depth along the deep fascial layer, which is predictive of necrotizing fasciitis 1. The high sensitivity of POCUS means it rarely misses cases, though specificity is somewhat lower, so positive findings should be correlated with clinical presentation.
Key Findings on POCUS
- Diffuse subcutaneous thickening
- Fluid accumulation of > 4 mm in depth along the deep fascial layer
- Fascial irregularity
- Subcutaneous edema
- Increased echogenicity of subcutaneous fat
Advantages of POCUS
- Can be performed rapidly at the bedside
- Does not delay surgical intervention
- High sensitivity for detecting necrotizing fasciitis
Limitations of POCUS
- Somewhat lower specificity (around 93.3%) compared to sensitivity
- Should not delay surgical consultation or debridement when necrotizing fasciitis is strongly suspected clinically, as early surgical intervention is crucial for improving survival in these rapidly progressing infections 1.
Clinical Correlation
POCUS findings should be correlated with clinical presentation, including signs and symptoms such as severe pain, swelling, and erythema, to increase the diagnostic accuracy for necrotizing fasciitis. The Laboratory Risk Indicator for Necrotizing infection (LRINEC) score can also be used to predict the presence of necrotizing soft-tissue infections, but recent evidence has demonstrated that it lacks the sensitivity to be a useful adjunct for the diagnosis of necrotizing infections 1.
From the Research
POCUS Necrotizing Fasciitis Sensitivity
- The sensitivity of Point-of-Care Ultrasound (POCUS) for diagnosing necrotizing fasciitis has been reported in several studies.
- A systematic review of the literature found that the overall sensitivity of POCUS for diagnosing necrotizing fasciitis ranged from 85.4%-100% 2.
- Another study found that POCUS had a high sensitivity and specificity for the diagnosis of necrotizing fasciitis, with fluid accumulation along the fascial plane being the most sensitive finding (85.4%; 95% CI 72.2% - 93.9%) 2.
- A prospective study found that POCUS images interpreted as concerning for necrotizing fasciitis had a high correlation with CT scan and/or surgical impression, suggesting a high sensitivity and specificity for POCUS in diagnosing necrotizing fasciitis 3.
- However, it is essential to note that the diagnosis of necrotizing fasciitis relies on clinical symptoms and signs, laboratory markers, and imaging, with the gold standard for diagnosis being intraoperative tissue culture 4.
Comparison with Other Imaging Modalities
- POCUS has been compared to other imaging modalities, such as computed tomography (CT) and magnetic resonance imaging (MRI), in the diagnosis of necrotizing fasciitis.
- A case report found that POCUS was able to diagnose necrotizing fasciitis in a patient who had negative CT and MRI findings 5.
- Another study found that ultrasonography was not recommended in adults due to the infiltration of the hypodermis blocking ultrasound transmission, but this was not specific to POCUS and may not be applicable in all cases 6.
Clinical Implications
- The high sensitivity and specificity of POCUS for diagnosing necrotizing fasciitis make it a valuable tool in the emergency department.
- POCUS can be used as an adjunct to clinical decision-making for the diagnosis of necrotizing fasciitis, allowing for prompt diagnosis and treatment 2, 3.
- However, it is crucial to remember that imaging studies should never delay emergency surgical treatment in patients with established necrotizing fasciitis 6.